Tutorial.ShftIn11 History

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February 06, 2007, at 11:42 PM by Carlyn Maw -
Added lines 65-76:

///// just needs the location of the data pin and the clock pin ///// it returns a byte with each bit in the byte corresponding ///// to a pin on the shift register. leftBit 7 = Pin 7 / Bit 0= Pin 0

byte shiftIn(int myDataPin, int myClockPin) {

  int i;
  int temp = 0;
  int pinState;
  byte myDataIn = 0;

  pinMode(myClockPin, OUTPUT);
  pinMode(myDataPin, INPUT);
February 06, 2007, at 10:28 PM by Carlyn Maw -
Changed line 5 from:

// Date : 25 Oct, 2006 //

to:

// Date : 25 Jan, 2007 //

February 06, 2007, at 10:21 PM by Carlyn Maw -
Changed lines 65-76 from:

///// just needs the location of the data pin and the clock pin ///// it returns a byte with each bit in the byte corresponding ///// to a pin on the shift register. leftBit 7 = Pin 7 / Bit 0= Pin 0 byte shiftIn(int myDataPin, int myClockPin) {

  int i;
  int temp = 0;
  int pinState;
  byte myDataIn = 0;

  pinMode(myClockPin, OUTPUT);
  pinMode(myDataPin, INPUT);
to:

//we will be holding the clock pin high 8 times (0,..,7) at the //end of each time through the for loop

//at the begining of each loop when we set the clock low, it will //be doing the necessary low to high drop to cause the shift //register's DataPin to change state based on the value //of the next bit in its serial information flow. //The register transmits the information about the pins from pin 7 to pin 0 //so that is why our function counts down

Changed line 76 from:
    digitalWrite(myClockPin, 0); 
to:
    digitalWrite(myClockPin, 0);
Added line 81:
      //set the bit to 0 no matter what
Changed line 86 from:
     //print statement  
to:
     //print statement since myDataIn starts as 0
Changed line 89 from:
to:
Changed line 98 from:
  //debuging print statements whitespace 
to:
  //debuging print statements whitespace
February 06, 2007, at 10:17 PM by Carlyn Maw -
Added lines 1-106:
//**************************************************************//
//  Name    : shiftIn Example 1.1                              //
//  Author  : Carlyn Maw                                        //
//  Date    : 25 Oct, 2006                                      //
//  Version : 1.0                                               //
//  Notes   : Code for using a CD4021B Shift Register    	//
//          :                                                   //
//****************************************************************

//define where your pins are
int latchPin = 8;
int dataPin = 9;
int clockPin = 7;

//Define variables to hold the data 
//for shift register.
//starting with a non-zero numbers can help
//troubleshoot
byte switchVar1 = 72;  //01001000

void setup() {
  //start serial
  Serial.begin(9600);

  //define pin modes
  pinMode(latchPin, OUTPUT);
  pinMode(clockPin, OUTPUT); 
  pinMode(dataPin, INPUT);

}

void loop() {

  //Pulse the latch pin:
  //set it to 1 to collect parallel data
  digitalWrite(latchPin,1);
  //set it to 1 to collect parallel data, wait
  delayMicroseconds(20);
  //set it to 0 to transmit data serially  
  digitalWrite(latchPin,0);

  //while the shift register is in serial mode
  //collect each shift register into a byte
  //the register attached to the chip comes in first 
  switchVar1 = shiftIn(dataPin, clockPin);

  //Print out the results.
  //leading 0's at the top of the byte 
  //(7, 6, 5, etc) will be dropped before 
  //the first pin that has a high input
  //reading  
  Serial.println(switchVar1, BIN);

//white space
Serial.println("-------------------");
//delay so all these print satements can keep up. 
delay(500);

}

//------------------------------------------------end main loop

////// ----------------------------------------shiftIn function
///// just needs the location of the data pin and the clock pin
///// it returns a byte with each bit in the byte corresponding
///// to a pin on the shift register. leftBit 7 = Pin 7 / Bit 0= Pin 0
byte shiftIn(int myDataPin, int myClockPin) { 
  int i;
  int temp = 0;
  int pinState;
  byte myDataIn = 0;

  pinMode(myClockPin, OUTPUT);
  pinMode(myDataPin, INPUT);

  for (i=7; i>=0; i--)
  {
    digitalWrite(myClockPin, 0); 
    delayMicroseconds(0.2);
    temp = digitalRead(myDataPin);
    if (temp) {
      pinState = 1;
      myDataIn = myDataIn | (1 << i);
    }
    else {
      //turn it off -- only necessary for debuging
     //print statement  
      pinState = 0;
    }

    //Debuging print statements
    //Serial.print(pinState);
    //Serial.print("     ");
    //Serial.println (dataIn, BIN);

    digitalWrite(myClockPin, 1);

  }
  //debuging print statements whitespace 
  //Serial.println();
  //Serial.println(myDataIn, BIN);
  return myDataIn;
}

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